grouting the block is fine,as long as your heads have been drilled for steam holes,but 406 s are notorious known for
trying to run hot,a good aluminum radiator
with a good'puller fan'works best,also,you will need to get an oil cooler,keep the temp low,your oil WILL break down faster
with the heat and bye bye 406,seen it happen a couple of times to those who thought they knew 400s....